Pressure, temperature, and speed control apparatus for supercharged combustion engines



Feb. 6, 1951 H. T. sPARRow 2,540,916

PRESSURE, TEMPERATURE, AND SPEED CONTROL APPARATUS EUR SUPERCEARGEDcoNEUsToN ENGINES y Filed Feb, l1, 1943 l 5 Sheets-Sheet 1 j y Snvento M/qo Gttorneg Feb. 6, 1951 Filed Feb. 1, 1945 H. T. SPARROW PRESSURE,TEMPERATURE, AND SPEED CONTROL APPARATUS FOR SUPERCHARGED COMBUSTIONENGINES 3 Sheets-Sheet 2 (Ittomeg Pah 6, i951 Filed Feb, l, 194i! H. SPA R RW PRESSUREv TEMPERATURE, AND SPEED CONTROL APPARATUS FORSUPERCHARGED COMBUSTION ENGINES 3 Sheets-Sheet 3 (Ittomcg Patented Feb.6, 1951 UNITED STATES PATENT OFFICE PRESSURE, TEMPERATURE, AND SPEEDCONTROL APPARATUS FOR SUPER- CHARGED COMBUSTION ENGINES Hubert T.Sparrow, Minneapolis, Minn., assignor to Minneapolis-Honeywell RegulatorCompany, Minneapolis, Minn., a corporation of Delaware ApplicationFebruary 1. 1943, Serial No. 474,378

tion of the pressure in the intake, sincethat pressure determines theamount of fuel in each charge reaching the combustion chamber orcylinders. In many cases where combustion engines are used, it isdesirable to maintain the output of the engine substantially constant,or to change it to a predetermined value. This is particularly true inthe case of combustion engines usedto drive the propellers of aircraft,wherein it is frequently desirable to maintain the engine constantly atits optimum power output. In order to maintain the power outputconstant, the intake pressure should be maintained constant. The intake'pressure is subject to variations due to several variable conditions,chief of which are variations in the external atmospheric pressure, andvariations in the position of the throttle.l Furthermore, some aircraftengines are provided with a compressor, or supercharger, driven by aturbine which is powered from the exhaust gases of the engine. The speedand hence the compression ratio of this compressor is usually controlledby a waste gate, which by-passes to the atmosphere a portion of theexhaust gases issuing from the exhaust manifold.

In an engine provided with a throttle and a supercharger controllable bya waste gate, the fuel supply to the engine is normally increasedfirstby moving the throttle toward its full open position, while the wastegate remains in itsfull open position and the supercharger or compressoris not operated. After the throttle has been moved to its full openposition, the fuel supplied to the engine may be further increased byclosing the waste gate gradually, thereby bringing the compressor intooperation and increasing the intake manifold pressure.

From the foregoing, it should be apparent that in order to provide acomplete system for controlling the intake manifold pressure of aninternal combustion engine wherein a turbinedriven compressor is usedfor supplying air under pressure to the carburetor, means must beprovided for controlling both the throttle andthe waste gate of theturbine driving the compressor, or other means which controls thecompression ratio of the compressor. v

Since the air passing through the compressor is heated by the act ofcompression. it is customarily passed through a heat exchanger, commonlytermed an after-cooler, after leaving the compressor, so asto increasethe density of the air as it enters theengine. The after-cooler does nottake all the heat out of the air, so that the air ,entering thecarburetor is warmer when the compressor is operating than when it isnot operating. Upon the occurrence of conditions which might cause theformation of ice in the carburetor, it is customary for the pilot of anaircraft to close the throttle slightly so as to reduce the intakemanifold pressure, and then to close the waste gate slightly so as tocause increased operation of the compressor, and hence an increasedtemperature of the air entering the carburetor, thereby inhibiting theformation of ice therein. By proper adjustment of the throttle and wastegate, the intake manifold pressure may be maintained constant Whileincreasing the temperature of the air supplied to the intake manifold.

Turbines of the type used commonly to drive the compressors associatedwith aircraft engines operate at very high speeds, in the neighborhoodof 20,000 revolutions per minute. The speed at which these devicesrotate is near the upper limits of permissible speed. Therefore, meansshould be provided for preventing the operation of the turbine at aspeed greater than a predetermined limiting value.

It is therefore an object of the present invention to provide animproved system for controlling the intake manifold pressure of aninternal combustion engine.

Another object of the present invention is to provide an intake manifoldpressure control system for an engine equipped with a compressor,including means for controlling the throttle position and means forcontrolling the compression ratio of the compressor.

Another object of the present invention is to provide a system forcontrolling the intake manifold pressure of an internal combustionengine, including means responsive to the intake manifold pressure, andmeans responsive to other compensating conditions.

Another object of the present invention is to provide, in an intakemanifold pressure control system, means for limiting the speed of acompressor used to supply compressed air to the A further oblect is toprovide an improved electrical proportioning control system forsequentially controlling the throttle and the compressor in an intakemanifold pressure control system.

A further object of the present invention is to provide an intakemanifold pressure control system in which a device for controlling thecompression ratio of a compressor is varied after a throttle positioningdevice has first been operated to move the throttle to full openposition.

A still further object is to provide, in such a system, an arrangementwhereby the throttle and the compression ratio controlling means may bemade to operate overlappingly rather than sequentially, so as toincrease the temperature of the air supplied to the intake manifoldwhile maintaining the pressure therein substantially constant.

Other objects and advantages of the present invention will becomeapparent from a consideration of the accompanying specification, claimsand drawing, in which:

Figure l represents, somewhat dlsgrammatically, an intake manifoldpressure control system embodying my invention,

Figure 2 represents a modication of the intake manifold pressure controlsystem of Figure l,

Figure 2a represents a portion of a modification of the system shown inFigure 2, and

Figure 3 represents, somewhat diagrammatically, a further modificationof the intake manifold pressure control system of Figure 1.

Figure 1 Referring to Figure l, there is shown an internal combustionengine I0, which may be the engine of an aircraft. Air for supportingthe combustion of fuel within the engine cylinders is supplied from anintake (not shown) which may be located in the leading edge of the wingof the aircraft, and passes through a duct II, a compressor I2 driven bya turbine I3, a duct I4, an after-cooler I5, and a duct I3 to acarburetor I1, where it is mixed with fuel from a. suitable source ofsupply (not shown). From thc carburetor I1, the fuel and air mixturepasses through a duct I8 in which a throttle valve 20 is located, anintake manifold 2I, a. duct 22, a compressor 23 which is driven throughgearing directly from the shaft 23 of the engine III, and a duct 24 tothe engine I0.

The compressor I2 is essentially a high speed fan, so that when thecompressor is stationary. the air may pass freely through it, with onlya relatively small amount of resistance due to friction. 'I'heafter-cooler I5 is a heat exchanger for removing the heat of compressionfrom the air discharged by the compressor I2. Cooling air from an intakenot shown in the drawing, and preferably located in the leading edge ofa wing of the aircraft, enters the after-cooler through a duct 25, andafter passing through a series of tubes or other heat exchangingstructure so that it absorbs some of the heat from the air discharged bythe compressor I2. passes through a duct 25 to an outlet which may belocated in the trailing edge of a wing of the aircraft.

The direct driven compressor 23 is also of the fan type, and since it isdriven by the engine III, its speed and hence its compression ratiovaries directly as the speed of the engine Il. 0n some types of aircraftengines, the direct driven compressor is an integral part of the engine,and serves not only as a compressor but 4 as a means for evenlydistributing the fuel and air mixture to the various cylinders.

Although I have shown the compressor 23 and the intake manifold 2| asseparate units, on most engines the direct-driven compressor is insidethe housing generally referred to as the intake manifold. They are shownseparately in the present diagrammatic disclosure merely for the purposeof simplifying the discussion.

Exhaust gases from the engine I3 pass through a duct 21 to an exhaustmanifold 23. From the exhaust manifold 23, the exhaust gases may passeither through a duct 30 controlled by a waste gate 3l to an outlet notshown in the drawing, or through a duct 32 to the turbine I3, and fromthe turbine I3 through a duct 33 to the discharge outlet. It may be seenthat when the waste gate 3l is open, the resistance to passage ofexhaust gases through the duct 30 is much lower than the resistance tothe passage of gasses through the duct 32 and turbine 33. Therefore,when the waste gate 3| is open, the turbine I3 is not operated. As thewaste gate is closed, the pressure in the exhaust manifold increases,until the pressure differential between the exhaust manifold and theoutside atmosphere is sumcient to cause rotation of the turbine I3.

The throttle 23 is driven by a motor generally ff f indicated at 34through a gear train 35, and a pair of bevel gears indicated at 36. Themotor 34 also drives a throttle follow-up potentiometer 31, whichcomprises a slider 38 movable along a slidewire resistance 40. The motor34 is shown, by way of example, as being of the direct current serieswound type, and includes an armature 4I and a pair of field windings 42and 43. As indicated by the legends in the drawing, energization of aseries circuit including armature 4I and field winding 42 causesrotation of the armature 4I in a direction to close the throttle and tomove the slider 38 of follow-up potentiometer 31 to the right alongresistance 40. On the other hand, energization of armature 4I and eldwinding 43 causes rotation of motor 34 in a direction to open thethrottle 20 and to move the slider 33 to the left along resistance 40.

The waste gate 3| is driven by a motor generally indicated at 44 througha gear train 45. The motor 44 also drives a waste gate follow-uppotentiometer 46, which comprises a slider 41 movable along a slidewireresistance element 43. The motor 44 is also of the direct current serieswound type, and is provided with an armature and a pair of fieldwindings 5I and 52. As indicated by the legend in the drawing, when thearmature 50 and field winding 5I are both energized, the armature 50rotates in a direction to drive the waste gate towards its open positionand to move the slider 41 to the right along resistance element 48. Onthe other hand, when the armature 50 and fleld winding 52 are energized,the armature 50 rotates in a direction to close the waste gate 3l and tomove the slider 41 to the left along resistance 43.

The energization of motors 34 and 44 is controlled by an electronicamplifier 53 and a cycling switch arrangement which includes acontinuously'running motor 54, cams 55, 56, 51 and 53 driven thereby,and switches 50, 5I, 62 and 53 operated by the respective cams.

The amplifier 53 may be of any suitable type. For example, I may use anamplifier of the type described in Figure 2 of the co-pending applical10n 0f Albert P- Upton, sei-iai No. 437,561, dated A9111 3. 1942. sincematured into Patent No.

2,423,534, issued July 8,1947.. The amplifier 53 includes a pair ofrelays 54 and 85. The relay 64 comprises a winding 56 which controls themovement ot a switch arm 81 cooperating with a stationary contact 68,with which it is engaged when the winding 66 is energized. Similarly,the relay 65 includes a winding 10 which controls the movement of aswitch arm 1| cooperating with a stationary contact 12,. with which itis engaged when the winding 18 is energized. As explained in the Uptonapplication previously referred to, the windings 66 and 10 areselectively energized by the amplier 53, in accordance with the phase oian alternating electrical signal potential applied to input terminals 13and 14 of amplier 53. The amplier 53 is supplied with electrical energyfrom an alternating current source through a transformer 15, whosesecondary winding is connected to power input terminals 16 and 11 ofamplifier 53.

The switch 60 comprises a switch arm 80 movable between an upperstationary contact 8| and a lower stationary contact 82. The switch 6|comprises a switch arm 83 movable between an upper stationary contact 84land a lower stationary contact 85. The switch 62 includes a. switch arm86 movable between an upper stationary contact 81 and a lower stationarycontact 88. The switch 63 includes a switch arm 80 movable between anupper stationary contact 8| and a lower stationary contact 82.

It should be readily apparent from an inspection of the drawing, that asthe motor 54 rotates the cams 55, 56, 51 and 58, the switches 60, 6|, 62and 63 are so operated that each switch arm engages its associated upperstationary contact during one-half revolution of the cam, and engagesits lower stationary contact during the other half revolution of thecam.

Only the switches 60 and 5| are concerned in the energizing circuits forthe motors 34 and 44. When the cams 55 and 56 are in a position such asthat shown in the drawing, wherein the switch arms 80 and 83 engagetheir respective upper stationary contacts 8| and 84, the waste gatemotor 44 is under the control of the relays 64 and 65 in the amplifier53. At such a time, an energizing circuit for field winding and armature50 of motor 44 may be traced from the left-hand terminal of a battery83, conductors 94 and 95, switch arm 1|, contact 12, a conductor 96,switch arm 80, contact 8|, a conductor 81, eld winding 5|, armature 50,and ground connections 98 and |00 to the opposite terminal of battery83. Similarly, an energizing circuit for field winding 52 and armature50 may be traced from the left-hand terminal of battery 83, throughconductors 84 and |0|, switch arm 61, contact 68, conductor |02, switcharm 83. contact 84, a conductor |03, field winding 52, armature 50, andground connections 88 and |00 to the right-hand terminal of battery 83.It may therefore be seen that at such a time, the armature 50 of motor44 is rotated in a direction dependent upon the phase o! an alternatingsignal potential impressed on the input terminals 13 and 14 of amplifier53.

During the half revolution of cams 55 and 58 when the switch arms 80 and83 engage their respective lower stationary contacts 82 and 85, thewaste gate motor 44 is no longer under control of amplifier 53, whichinstead controls throttle motor 34. At such a time, an energizingcircuit for ileld winding 42 and armature 4| of motor 34 may be tracedfrom the lefthand terminal of battery 8l through conductors 84 and 85,switch arm 1|, contact 12, conductor 86, switch arm 80, contact 82, aconductor |04, field winding 42, armature 4|, and ground connections |05and |00 to the right-hand terminal of battery 83. Similarly, anenergizing circuit for field winding 48 and amature 4| may be tracedfrom the left-hand terminal of battery 83 through conductors 84 and |0|,switch arm 61, contact 68,'conductor |02, switch arm 83,

l contact 85, a conductor |06, field winding 43,

armature 4|, and ground connections |05 and |00 to the right-handterminal of battery 83. Since the relays 64 and 65 of amplier 53 areselectively energized in accordance with the phase of an alternatingsignal applied to input terminals 13 and 14, it may be seen that themotor 34 is rotated in a direction dependent upon the phase of thesignalapplied to those input terminals.

The input terminals 13 and 14 of amplier 53 are supplied with analternating signal potential of a given phase or of the opposite phase,depending upon the direction of unbalance of an electrical network ofthe Wheatstone bridge type, having a pair of input terminals ||0 and andthree output terminals ||2, ||3 and ||4. This bridge circuit is suppliedwith electrical energy from a transformer ||5V whose secondary windingis connected to the input terminals 0 and through conductors ||6 and 1,respectively.

The upper left arm of the bridge circuit, as it appears in the drawing,connects input terminal ||0 with output terminal ||2, and may be tracedfrom input terminal ||0 through a conductor ||8, contact 8|, switch arm80, a conductor |20, a slider |2| and a portion of a cooperatingresistance element |22, a conductor |23, a slider |24, a resistanceelement |25 and a contact |26 which cooperate with slider |24, aconductor |21, a slider |28, a resistance element |30 which cooperateswith slider |28, a conductor |3|,v a slidewire resistance element |32and a slider |33 which cooperates therewith to output terminal ||2,which is located on slider |33.

The upper right arm of the bridge circuit, as it appears in the drawing,connects the input terminal with .output terminal ||2. This arm may betraced from input terminal through a conductor |34, a fixed resistance|35. a conductor |36, a portion of resistance |32 and slider |33 tooutput terminal ||2.

'I'he bridge output terminal ||2 is connected through a conductor |31 tothe input terminal 14 of ampliiier 53. Bridge output terminal |i3 isconnected through a conductor |38 to upper stationary contact 81 ofswitch 62.' Output' terminal ||4 is connected through a conductor |40 tolower stationary` contact 88 of switch 62. When switch arm 86 engagesthe upper terminal 81, then terminal ||3 serves as the output terminalof the bridge circuit, and when switch arm 86 engages contact 80, thenterminal ||4 serves as the output terminal4 of the bridge circuit.Either output terminal ||3 or 4, depending upon the position of switcharm 86, is connected through switch arm 86 and a conductor |4| to oneterminal of a resistance element |42 whose opposite terminal isconnected to the conductor |31. 'A tap |43 movable along resistance |42is connected directly to input terminal 13 of ampliiler 53.

Since, when the parts are in the positions shown in the drawing, theterminal ||3 is acting as the second output terminal'of the bridgecircuit, the lower left arm of the bridge circuit; may be considered asincluding those elements which interconnect input terminal with outputterminal ||3. This lower left arm may therefore be traced from inputterminal ||0 through a fixed resistance |44, a conductor |45, resistance46 and the slider 46 to output terminal ||3. Similarly, the lower rightarm of the bridge circuit may be traced from input terminal through afixed resistance |06, a conductor |41, resistance element 40, aconductor |46, and Slider 41 to output terminal I I3.

A variable resistance |50 is connected in parallel with the resistance46. Adjustment of resistance |50 determines the total potential dropacross resistance 46, and hence determines the potential drop per unitlength of resistance 46. Similarly, a variable resistance |5| isconnected in parallel with the resistance 40 of the throttle follow-uppotentiometer 31.

The slider |33 and resistance element |32 to gether form a controlpotentiometer |52. The slider |33 is moved along the resistance |32 inaccordance with the absolute pressure existing in the intake manifold2|. A flexible bellows |53 has its interior connected through a tube |54with the intake manifold 2|, so that the pressure existing inside themanifold 2| is transmitted to the inside of the bellows |53. One end ofthe bellows |53 is fixed, and its other end is connected through a link|55 to the slider |33. Another bellows |56 is evacuated. The bellows |56is also fixed at one end, and its free end is connected to the end oflink |55 opposite the bellows |53. Atmospheric pressure exists adjacentthe outside surfaces of both bellows |53 and |56. When a change inatmospheric pressure occurs, the forces produced by the two bellows onthe link |55 oppose each other, so that no motion of slider |33 rLsults.However, if the pressure in the intake manifold 2| changes, the bellows|53 expands or contracts without opposition from bellows |56 other thanthat caused by its normal spring rate, and the slider |33 is moved overthe resistance |32. Therefore it may be seen that the position of slider|33 with respect to resistance |32 is a measure of the absolute pressureexisting within the intake manifold 2|.

The slider |26 and the resistance element |30 together form acompensating controller |60. The slider |26 is movable along resistance|30 by means of a bellows |6|, whose interior is connected by a tube |62to the exhaust manifold 26. The bellows |6| is fixed at one end, and itsopposite end is connected by a link |63 to the slider |26. An evacuatedbellows |51 acts on the 0pposite end of link |63 to compensate theaction of bellows |6| for variations in atmospheric pressure, in thesame manner that evacuated bellows |66 compensates the action of bellows|63, as described above. Since the interior of bellows |6| is suppliedwith pressure from the exhaust manifold 26, and its action iscompensated for variations in atmospheric pressure, by means of bellows|61, it may be stated that the position of slider |26 is a measure ofthe absolute pressure existing in the exhaust manifold 26. This pressuredifferential is in turn a measure of the power being delivered to theturbine. The slider |23 is biased into engagement with a stop |64 by aspring |12. The tension of spring |12 may be adjusted by rotation of ascrew |13 which threadedly engages a stationary member |14. Adjustmentof screw |13 determines the particular value of pressure in the exhaustmanifold 26 at which the controller |60 begins to insert resistance inthe bridge circuit. During the normal range of pressure in the exhaustmanifold 26, the slider |20 rests against stop |64 at the right end ofits range of movement. At such a time, none of the resistance |30 isconnected in the upper left arm of the bridge circuit. When the exhaustback pressure increases to a value which represents the top safe backpressure for reliable engine operation, the bellows |6| starts to movethe slider |26 across resistance |30, thereby inserting part of theresistance |30 in the bridge'circult.

The slider |24 and the cooperating resistance element |26 and contact|26 together form a second compensating controller |66. The slider |24is moved along contact strip |26 and resistance |26 by a governor deviceschematically indicated at |66. in accordance with the speed of shaft I6of turbine I3. The governor |66 and the controller |66 are so relatedthat in the normal speed range of the turbine, the slider |24 engagesthe contact strip |26, and hence introduces no resistance into thebridge circuit. As the shaft I6 approaches its limiting speed, thegovernor |66 moves the slider |24 along the resistance |25 to insert anincreasing amount of resistance into the bridge circuit.

The slider |2| is movable along resistance |22 by a manually operableknob |66. The knob |66, slider |2| and resistance |22 together form acontrol point adjuster |61. This device is located in a position whereit may be controlled by the pilot or some other member of the crew ofthe aircraft. Movement of slider |2| by means of knob |69 determines thevalue of the pressure within the intake manifold 2l which the systemwill maintain.

When cam 66 is in such a. position that switch arm 60 of switch 63engages the lower stationary contact 32, the upper left arm of thebridge circuit may be traced from input terminal I|0 through a portionof conductor H6. a normally closed switch |66, a conductor |10, andlower stationary contact 32 to switch arm 60, and hence as before tooutput terminal ||2 `of the bridge circuit. When the switch |66 is open.this portion of the bridge circuit also includes a variable resistance|1|, which is normally shunted by the switch |66. The switch |66 may bemanually operated, or it may be automatically operated by a device |14responsive to the presence of icing conditions. One such device suitablefor this purpose is the one disclosed in the co-pending application ofWaldo H. Kliever. Serial No. 463,259, filed October 24, 1942. sinceissued as Patent No. 2,432,669, dated Dec. 16, 1947. The switch |66 ofthe present application may be for example the switch |33 of Figure 14of the Kliever application. If any other ice detecting mechanism isemployed. the switch |66 will be actuated by any element thereof movablein accordance with the presence or absence of ice or ice producingconditions.

Operation of Figure-1 From the foregoing description it should beunderstood that the bridge circuit, through the amplifier 63,alternately controls first the waste gate motor 44 and then the throttlemotor 34. This alternate control of the two motors is effected byoperation of the switches and 6| by the continuously running motor 64.Furthermore, because of the operation of the switch l2, when the andereference between the output terminals H2 and H4 l is impressed on theamplifier input terminal.

Consider first the condition existing when the amplifier 53 iscontrolling the throttle motor 34. Assume that the pressure in theintake manifold is such that the bridge circuit is balanced when thethrottle is half way open, and the throttle follow-up potentiometer 31is therefore in its center position, as shown in the drawing. 'I'hebridge circuit is said to be balanced when no potential differenceexists between the output terminals, in this case, terminals ||,2 andH4. When no potential difference exists between these terminals, nopotential is impressed on the input terminals 13 and 14 on the amplifier53. Hence neither of the relays 64 and 65 is energized, and the throttlemotor therefore remains stationary.

With the same conditions existing in the system, consider the operationwhich takes place when the amplifier 53 is controlling the waste gatemotor 44. At such a time, the potential difference between outputterminal H2 and output terminal H3 is impressed on the input terminal ofampliner 53. Since slider 38 is at the same potential as input terminalH2, the potential then impressed on the amplifier input terminal isequal to the potential drop along the resistance 40 between the slider38 and the left terminal of resistance 40.

For the sake of convenience in describing the operation of this system,consider that the operation is taking place during a half cycle when aleft end of the secondary winding of the transformer H5 is positive, andits right terminal is negative. During the alternate half cycles, thepolarity of any specific potential 'is opposite to that described.

It will therefore be seen that, with the various parts in the positionsshown in the drawing, the difference of potential between outputterminals H2 and H3 of the bridge circuit is of a polarity such thatterminal H3 is positive with respect to terminal H2. As this potentialis applied to the input terminals of amplifier 53, its polarity is suchthat input terminal 13 is positive with respect to input terminal 14.The amplifier 53 is so connected that it responds to a potential of thispolarity, or phase. by energizing winding of relay 65. Energization ofwinding 10 causes switch arm 1| to engage contact 12, thereby completingthe energizing circuit, previously traced, for field winding 5| andarmature 50 of waste gate motor 44. Energization of this field windingand the armature causes the motor 44 to run in a direction to open thewaste gate. However, the waste gate is already fully open, and the wastegate follow-up potentiometer 46 has reached the limit of its movement inthe gate opening direction. Therefore the motor 44 is merely stalledagainst a stop (not shown) associated with the waste gate, and nooperation of the control system results.

It may therefore be seen that as long as the intake manifold pressureremains at the value which the system has been set to maintain, thewaste gate and throttle remain at the positions indicated by thepositions of their respective followup.potentiometers in the drawing.

Now let it be assumed that the pressure in the intake manifold steadilydecreases, such as might io 6 occur if the aircraft climbs steadily togain altitude. The decrease in pressure in the intake .manifold causesthe bellows |53 to contract.

thereby moving the slider |33 tothe left acrossresistance |32. `Thepotential of output terminal H2 then becomes more positive than thepotential of output terminal H4. Therefore, during the time when theamplifier 53 is in controlof the throttle motor. a potential isimpressed on the input terminals 13 and 14 of a polarity such thatterminal 14 ispositive with respect to terminal 13. When a potential ofthis polarity is applied to the amplifier input terminals, the amplierresponds to energize relay winding 66 of relay 64. Energization of relay64 causes the completion of an energizing circuit for field winding 43and armature 4I of throttle motor 34. The motor then operates in adirection to open the throttle and to move the slider 38 to the leftalong resistance 40. Asa result of this opening movement of thethrottle, the intake manifold pressure is increased to restore it towardits original condition, and at the same time the throttle follow-uppotentiometer 31 is operated to reduce the unbalance potential of thebridge circuit.

If the pressure in the intake manifold 2| continues to decrease afterthe throttle is fully open, the field winding 43 of throttle motor 34continues to be energized each time that the throttle motor is placedunder control of amplier 53. Since the throttle has reached its fullyopen position, the motor 34 stalls against a stop, not shown in thedrawing, associated with the throttle mechanism. However. when the`throttle is fully open and the pressure in the intake manifold continuesto decrease, then, during each time that the amplier 53 controls thewaste gate motor 44, a signal is applied to the input terminais ofamplifier 53 of a polarity such as to cause energization of relay 64.This causes energization of winding 52 and armature 50 of waste gatemotor 44, running the motor in a direction to close the waste gate andto move the slider 41 to the left along resistance 43 so as toyrebalance the bridge circuit. It may therefore be seen that, for agiven setting of the control point adjuster |61. the positions of thethrottle and waste gate bear a definite predetermined relation to thepressure in the intake manifold, and that for each change in the intakemanifold pressure a proportionate change takes place in either thethrottle or waste gate positions. In other words, the throttle and wastegate are controlled in a modulating manner.

Closure of the waste gate 3| increases the pressure differential acrossthe turbine i3, and thereby causes the turbine to rotate, driving thecompressor to increase the pressure of the air supplied to the intakemanifold. If the pressure in the intake manifold continues to decreasedue to increasing laltitude of the aircraft, the waste gate is closedmore and more, thereby increasing the pressure differential across theturbine, increasing the turbine and compressor speed, and hence thecompression ratio of the Acompressor so as to restore the pressure inthe intake manifold to its desired value.

Conversely, it should be apparent from the foregoing that upon acontinued increase in intake manifold pressure, the system first movesthe waste gate to fully open position, thereby stopping the compressor,and then starts closing the throttle.

The compensating controller acts to introduce resistance into the upperleft arm of the' bridge circuit whenever the pressure in the exhaustmanifold rises above a predetermined value. The purpose of thiscontroller is to prevent the exhaust manifold pressure from rising 12opentoiullclosedpositionasthepressureis varied further over anotherinchof mercury.

operation. The compensating controller |80 prevents such a conditionfrom occurring. When the controller Ill acts. upon an increase inexhaust pressure, to introduce resistance into the upper left arm of thebridge. the bridge is thereby unbalanced in the same sense as if anincrease in the intake manifold pressure had occurred. The systemresponds to such an unbalance by opening the waste gate sumciently torelieve the prsure in the exhaust manifold.

It is desirable to provide means for preventing overspeeding of theturbine. Such a means is provided in the compensating controller |85,which is operated by a governor device |06 to increase the resistance inthe upper left arm of the bridge circuit when the sneed of the turbineI3 exceeds a predetermined value. As previously described, upon such anunbalance of the bridge circuit. the system responds to open the wastegate and lower the manifold Ipressure the correct amount as dictated bythe top safe speed of the turbine.

The position of slider |33 of control potentiometer Il! shouldaccurately reflect the pressure in the intake manifold as that pressurevaries over a wide range. It has been found in practice that a range offrom 17 to 46 inches of mercury includes most pressure conditionsencountered. The control potentiometer |52 should therefore beconstructed so that a variation in pressure of 29 inches of mercurycauses movement of the slider |23 from the rieht extremity of theresistance |22 to the left extremity. It is generally desirable tomaintain the intake inanii'old pressure in a range. hereinafter termedthe "tbrottling range, which lies within one inch of mercury more orless of any selected pressure within the wide range. The throttle andwastegate L should therefore be sequentially moved throughout their fullrangeL as the intake manifold pressure varies through an operating rangeof two inches of mercury. In order to secure such operation. totaleffective resistance of the slidewires I and la and their respectiveparallel resistance and |50 should be *ha of the resistance of element|32. The throttling range. or the range within which the system willmaintain the manifold pressure. may be adjusted by varying theresistances llt and ill. so as to vary the total effective resistancebetween the opposite terminals of the two follow-up potentiometers inproportion to the resistance of element |32. Furthermore. by relativelyvarying the two resistances |50 and IBI, the proportion of the totalthrottling range during which the throttle is moved may be varied withrespect to the portion of the total throttling range during which thewaste gate is controlled. For example, under certain conditions, it maybe desired to move the throttle from full closed to full open positionas the intake manifold pressure varies over a range of one inch ofmercury. and after the throttle is fully opened to move the waste gatefrom full position, as described above.

On the other hand. it may be desirable to move the throttle from fullclosed to full open position as the intake manifold pressure varies overonly l/z inch of mercury. and thereafter to move the waste gate fromfully open to fully closed position as the manifold pressure variesfurther over a range of 1% inches of mercury. A change from one of thesemodes of operation to the other may be accomplished by varying theresistances |50 and lli from a nrst setting in which the totalresistance of the two elements Ilii and 48 equals that of the twoelements IBI and I0 to a second setting in which the total resistance ofthe elements |50 and ll is three times that of the two elements ill andlll.

In order that the pilot may move the throttling range of two inches toany part of the wide range of 29 inches of mercury over which the systemcan operate, the resistance of element |22 should be chosen so that itseffect on the bridge circuit is comparable tothat of control resistance|32. The compensating controller should have its resistance |30 soproportioned that it will introduce resistance into the bridge circuitat a rate which will effect the desired control of exhaust backpressure.

The resistance |25 inthe compensating controller |65 should berelatively high, so that it will be effective to absolutely preventincreases in speed of the turbine I3 above a predetermined limitingvalue.

The most emcient method of operation of the throttle 'and waste gate isto first open the throttle wide and then to gradually close the wastegate in order to increase the intake manifold pressure. This mode ofoperation may be termed szquential control of the throttle and wastegate. It may sometimes be desirable. however, to control the throttleand waste gate overlappingly rather than sequentially. Morespecifically, it may ce desired to partially close the throttle and atthe same time close the waste gate partially so as to increase thecompression ratio of the compressor, thereby increasing the tempzratureof the air supplied to the carburetor due to the heat of compression.The latter mode of operation is especially desirable when thetemperature conditions are such that there is a possibility of theformation of ice in the carburetor. I have therefore provided in thesystem of Figure 1, vmeans whereby this latter mode of operation may beaccomplished. The switch |68 is normally closed, and when so closed, thethrottle and waste gate are operated sequentially toward their pressureincreasing When the switch |38 is opened, which may either be donemanually, or at the command of some device responsive to the presence oficing conditions, the resistance is inserted in the upper left arm ofthe bridge circuit each time that the amplifier B3 is controlling thethrottle motor 3l. This increased resistance in the upper left arm ofthe bridge circuit causes a change in its output potential of the samenature as that which would occur upon an increase in pressure in theintake manifold. Therefore the amplifier 53 responds to this potentialby energizing field winding I2 and armature 4| of the throttle motor, soas to run the throttle toward closed position. This movement of thethrottle causes a decrease in the pressure in the intake manifold. sothat when the system is next put in control as in Figure l.

of the waste gate motor, the bridge circuit is unbalanced in a directionwhich causes the waste gate to close by an additional amount, therebyincreasing the speed of the turbine and hence the compression ratio ofthe compressor. When the compression ratio is increased the temperatureof the air supplied to the carbu-v retor is increased', so as to meltany ice which may have formed there and to prevent the formation offurther ice. Also, the resulting increase in pressure restores theintake manifold pr-.ssure to its desired value. Therefora the systemaccomplishes a pressiilreily decreasing movement of the throttle and"ad, mpensating pressure increasing movement of lth \\w\aste gate, sothat the pressure in the intake manifold is maintained substantiallyconstant, but the temperature of the air supplied to the carburetor ismaterially increased. By adjusting the resistance Ill, the amount ofthepressure decreasing movement oi the throttle, and hence thecorresponding pressure increasing movement of the waste gate may becontrolled within the limits of allowable exhaust back pressure ascontrolled by compensator |60. In this manner, the amount of heatsupplied to the carburetor for de-icing purposes may be varied inaccordance with the severity `of the icing conditions encountered. It isin connection with this deicing operation that the compensator |60 isparticularly valuable, since the exhaust pressure is at such times moreapt to rise to undesired values.

summarizing the operation of the system of Figure l, the throttle motorand the waste gate motor are sequentially controlled in response to thepressure in the intake manifold, in such a manner as to maintain theintake manifold pressure within a predetermined range of values. Meansare provided, which respond to the exhaust back pressure to prevent thatexhaust back pressure from increasing suiliciently to cause damage to-the engine, even though a reduction in the intake manifold pressure maybe required to produce this result. Further means are provided, whichrespond directly to the speed of the turbine to modify the control ofthe waste gate so as to prevent it from reaching an unsafe speed. Meansare also provided to control the throttle and waste gate motorsoverlappingly instead of sequentially, so as to take advantage of ltheheat of compression of the air passing through the compressor to preventthe formation of ice in the carburetor. This last means may be operatedeither manually by the pilot or automatically at the command of a deviceresponsive to the presence of icing conditions in the atmosphere or inthe carburetor itself. Thus, the present apparatus includes meansresponsive to engine operating variables and means controlled therebyfor maintaining or changing the values of said variables.

Figure 2 In Figure 2 is shown a modification of the control system ofFigure l. In the system of Figure 2, the engine, its combustion airsupply system, and its exhaust gas discharge system are the same Also,the bridge circuit and the motors which control the throttle and wastegate are 'substantially the same as in the system of Figure l. The meansby which the unbalance of the bridge circuit controls the throttle andwaste gate motors is quite different however, and a different method ofintroducing overlappini operationV of the throttle and waste gate toprevent icing in the carburetor is shown. Those elements in the systemof Figure 2 which are the same as corresponding elements of Figure 1have been given the same reference character, and will not be furtherdescribed in detail. Elements of the system of Figure 2 which aredifferent from any shown in the system of Figure l have been givenreference characters in the 200s.

Referring to the bridge circuit of Figure 2, it may be seen that this issubstantially identical with vthe bridge circuit of Figure l, the onlydifference being that the conductor |20 now connects slider |2| of thecontrol point adjuster |61 directly to the input terminal |0 of thebridge clrcuit. The switches 63 and |60 and resistance 1| are notpresent in the circuit of Figure 2.

Instead of a single amplifier and cyclically operated switching meansfor alternately transferring the amplifier from control of the wastegate motor to control of the throttle motor, there'are provided in thesystem of Figure 2 two separate amplifiers, one for controlling thewaste gate motor and one for controlling the throttle motor. The wastegate amplifier is numbered 200 in the drawing and the throttle amplifieris numbered 235. Each of the amplifiers 200 and 235 may be of the sametype as the amplifier 53 of Figure l. The waste gate amplifier 200 has apair of input terminals 20| and 202. The input terminal 202 is connectedthrough a conductor 203 and a conductor 204 to bridge output terminalII2. The conductor 203 is connected through a resistance 205, acondenser 206, and a conductor 201 to bridge output terminal ||3. A tap208 associated with resistance 205 is connected directly to amplifierinput terminal 20|. It may therefore be seen that any alternatingpotential occurring between bridge output terminals I2 and ||3 isimpressed through condenser 206 across resistance 205. A portion of thispotential, depending upon the position of tap 208, is impressed on theinput terminals 20| and 202-of waste gate amplifier 200. The amplifier200 is supplied with electrical energy from a transformer 2|2, andincludes a pair of relays 2|0 and 2|I, which are selectively energizedin accordance with the phase of the potential supplied to the inputterminals 20| and 202. The relay 2|0 controls the position of a switcharm 2|3 which cooperates with a stationary contact 2H in such a mannerthat the switch arm engages the contact when the relay is energized.Similarly, the relay 2|| controls the position of a switch' arm 2|5which cooperates with a'stationary contact 2|6 in such a manner that theswitch arm engages the contact when the relay is energized.

Switch arm 2|3 controls an energizing circuit for field winding 5| andarmature 50 of motor 44. which circuit may be traced from the left-handterminal of a battery 2|1 through conductors 2 I0 and 220, a stationarycontact 22|, a switch blade 222, a conductor 223, switch arm 2|3,contact 2 I4, a conductor 224, a contact 225 and its associated switchblade 226, a conductor 221, field winding 5|, armature 50, and groundconnections 228 and 230 to the opposite terminal of battery 2li.

The relay 2|| controls an energizing circuit for field winding 52 andarmature 50 of motor M. which circuit may be traced from the leftterminal of battery 2|1 through conductors 2|8 and 220, contact 22|,switch blade 222, conductor 223, switch arm 2|5, contact 2|6, conductor23|, stationary contact 232 and its associated switch blade 233, aconductor 234, field winding 52, armature 58, and ground connections 228and 238 to the right hand terminal of battery 2|1.

The throttle amplifier 235 has a pair of input terminals 238 and 231.The input terminal 231 is connected through a conductor 238 andconductor 284 to output terminal ||2 of the bridge circuit. Conductor238 is connected through a resistance 248. a condenser 24|, a conductor242. contacts 21| and 212 of a normally closed switch 243, and aconductor 244 to output terminal ||4 of the bridge circuit. It may beseen that any potential diil'erence occurring between output terminals||2 and ||4 of the bridge circuit is impressed through condenser 24|across the resistance 248. A portion of this potential, depending uponthe position of a tap 245 associated with the resistance 248 is appliedto the input terminals 238 and 231 of amplifie;` 235. The amplifier 235is supplied with electrical energy from a transformer 246, and includesa pair of relays l24'! and 248, which are selectively energizeddepending upon the phase of the electrical potential supplied to theinput terminals of the amplifier. Relay 241 controls the movements of aswitch arm 258 with respect to a stationary contact 25|. Relay 248controls the movements of a switch arm 252 with respect to a stationarycontact 253. Switch arm 258 controls an energizing circuit for winding42 and armature 4| of throttle motor 34. This circuit may be traced fromthe left-hand terminal of battery 2 I1 through switch arm 258, contact25|, a conductor 254, a contact 255 and its associated switch blade 256,a conductor 251, f'leld winding 42, armature 4| and ground connections258 and 238 to the opposite terminal of battery 2 1.

The switch arm 282 controls an energizing circuit for field winding 43and armature 4| of motor 34, which may be traced from -the lefthandterminal of battery 2 I 1 through switch arm 252, contact 253, aconductor 268, a stationary contact 26| and its associated switch blade262. a conductor 263, eld winding 43, armature 4|, and groundconnections 258 and 238 to the righthand terminal of battery 2|1.

The contact 225 and the switch blade 226 together comprise a limitswitch 264 which is biased to closed position. and is operated to openposition by an extension 265 on slider 41 when the waste gate reachesits fully open position. The contact 232 and the switch blade 233comprise a limit switch 266 which is biased to closed position, and isopened by the extension 265 on blade 41 when the waste gate 3| reachesits fully closed position.

The contact 255 and the associated switch blade 256 together form alimit switch 261, which is operated by an extension 268 on slider 38when the throttle reaches its closed position. The contact 26| andswitch blade 262, and the contact 22| and switch blade 222 together forma dual switch 218. The switch 218 is biased to the position shown in thedrawing, in which blade 262 engages contact 26| and blade 222 is spacedfrom contact 22|. The dual switch 218 is operable by engagement ofextension 268 with switch blade 262 when the throttle moves to its fullyopen position, so that the switch blade 262 is disengaged from contact26| and switch blade 222 is moved into engagement with contact 22| 'I'heswitch blade 262 and contact 26| serve as a limit switch in theenergizing circuit for winding 43 of motor 34, while the switch blade222 and contact 22| serve as a transfer switch to put the lili - 16bridge circuit in control of the waste gate motor when the throttlereaches its fully open position.

Each of the four limit switches 264, 286, 281. and 28|, 282 function toopen one of the motor energizing circuits so as to prevent furtherenergization of the motor for operation in a given direction after thedevice driven by the motor has reached its limiting position in thatdirection. This prevents waste of electrical energy due to such uselessenergization of the motor windings. and also prevents strain on themechanical parts driven by the motor. and adverse effects due to heatingof the motor windings.

The transfer switch 22|, 222 in dual switch 218 serves to prevent anyenergization of the waste gate motor as long as the throttle is in anyposition except its fully open position.

When the switch 243 is in the position shown in the drawing. itcompletes a circuit between contacts 21| and 212, as previouslydescribed. When it is moved to the right from the position shown in thedrawing, it completes a circuit between contact 213 and 214, therebyshunting the transfer switch 22|, 222 in the dual switch 218.

'I'he switch 243 may be manually operated, or may be operated by somedevice 214 responsive to the presence of ice forming conditions, such asthe device shown in the co-pending Kliever application previouslyreferred to.

A bridge circuit 215 has xed resistances 216, 211 and 218 in three ofits arms, and in its fourth arm is a resistance element 288, of nickelor some other material having an appreciable temperature coefiicient ofresistance. The resistance element 288 is located in the path of the airentering the carburetor I1. The bridge circuit 215 is ysupplied withelectrical energy from a transformer secondary winding 28|. Theresistance elements 218, 211, 218 and 288 are so proportioned that thebridge circuit 215 is balanced when the temperature of the air in thecarburetor is approximately 90 F. The output terminals of bridge 213 areconnected through conductors 282 and 283 respectively to the switchcontacts 21| and 212. When the switch 243 is in the position shown inthe drawing, the contacts 21| and 212 are shunted and the outputpotential of the bridge 215 has no eifect on the control system. Whenthe switch 243 is moved to the right from the position shown in thedrawing however, the output potential of bridge 215 is connected inseries with the potential between output terminals ||2 and ||4 of themain bridge. The transformer ||5 and transformer secondary winding 28|are supplied with electrical energy from the same source, so that theoutput potential of the two bridges are either in phase with each other,or opposite each other in phase. Hence the potential supplied to theinput terminals 236 and 231 of the throttle amplifier 235 is a portionof the algebraic sum of these two bridge output potentials. Thepolarity, or phase, of the output potential of bridge 215 is such thatwhen the carburetor air temperature is below 35, it introduces a signalinto the throttle arnpiifier of a phase such as to cause the amplifierto energize relay 241, thereby operating the throttle towards closedposition.

Operation of Figure 2 When the parts are in the position shown in thedrawing, the waste gate is fully open, and the throttle is half-wayopen, as indicated by the positions of the follow-up potentiometers 417s and 31. respectively. The transfer switch 22|,

222 is then opened, so that the waste gate amplifier 200 does not,control the motor 44. The throttle amplifier 235 and hence the throttlemotor 34, is under control of the main bridge circuit, but thecarburetor temperature responsive bridge circuit 215 is shuntedy by theswitch 242.

Under these conditions. let it be assumed that the pressure in theintake manifold 2| decreases gradually from the value determined by thesetting of the control point adjuster I61. Because of this decrease inpressure, the bellows |53` collapses, moving the slider II2 to the leftalong resistance |32. A potential difference is thereby created betweenoutput terminals II2 and II4 of the bridge circuit, which is impressedon theJ input terminals of the throttle amplifier 235, and which is ofthe proper phase so that the ampliiler energizes the relay 240, therebymoving switch arm 252 into engagement with contact 253 and completingthe energizing circuit for field winding 43 and amature 4I of throttlemotor 34, previously traced. This energization of motor 34 drives'thethrottle toward open position and moves the slider to theleft alongresistance 40. As the intake manifold pressure continues to decrease,the throttle is opened wider until it reaches its fully open position.When the latter position is reached, the extension 268 on slider 38engages switch blade 262, thereby opening the limit switch in thecircuit of field winding 43 and operating the transfer switch 22|, 222to place the waste gate motor 44 under control of the main bridgecircuit. Thereafter, if the pressure in the intake manifold continues todecrease, the waste gate amplifier 200 responds to the unbalance of thebridge circuit to cause energization of field winding 52 and armature 50of motor 44. Such energization of motor 44 drives the Waste gate towardsits closed position, thereby increasing the pressure diierential acrossthe turbine I3 and causing operation of the compressor I2 to increasethe intake manifold pressure.

Upon an increase ririfiritake manifold pressure, the system firstoperates the waste gate to its fully openepsition, thereby stopping thecompression, and then gradually closes the throttle.

When the switch 243 has been moved rto its right-hand position, and thetemperature in the carburetor I1 is below 35, a signal is introducedinto the input circuit of amplifier 235 in the proper sense to causethrottle motor 34 to drive the throttle towards closed position. Thisdecreases the pressure in the intake manifold, causing a response of thewaste gate motor to drive the waste gate toward its closed position,thereby restoring the pressure in the intake manifold to its desiredvalue, and utilizing the heat of compression of the air passing throughthe compressor I2 to raise the temperature in the carburetor I1. Itshould be noted that the waste gate motor is always under control of thebridge circuit when the switch 243 is operated to its right-handposition, regardless of the position of the throttle at that time.

When the system has been operating the waste gate and throttleoverlappingly, and the switch 243 is operated to its left-hand position,it is possible that the waste gate may be left in an intermediateposition, from which it cannot move because the transfer switch 22|, 222is open, since the throttle is also in an intermediate position. Toovercome such a condition, the pilot should, after operation of theswitch 243 to its left position. operate the control point selector |61in a pressure increasing direction far enough to open the throttle wide,thereby placing the waste gate under control of the bridge. The pilotmay then restore the control point selector to its previous position,and the system will respond by opening the waste gate wide and thenclosing the throttle.

Figure 2A matic. This arrangement is shown in Figure 2A.

Figure 3 In Figure 3 I have shown a simplified modification of thecontrol system illustrated in Figure l, in which only the superchargerwaste gate is controlled automatically, the throttle being under manualcontrol. In thismodification, the compensating controller |65 which isoperated in accordance with the speed of the turbine is y omitted. Inthis modification also, I have shown an arrangement whereby the wastegate motor may be controlled either automatically in accordance with thecarburetor intake pressure, or manually by the pilot.

In Figure 3, the engine, its intake and exhaust system, and the mainbridge circuit are substantially the same as those in the previousfigures,

- and the elements in Figure 3 which correspond to similar elements inFigure 1 have been given the same reference numerals. Those elements inFigure 3 which do not correspond to any element in Figure 1 have beengiven reference numerals in the 300 series.

Referring to Figure 3, it may be seen that the throttle 20 iscontrolledby a manual lever 300, through a linkage not shown in thedrawing. The waste gate motor 44 is controlledby an amplifier 30|, whichmay be of the same type as the amplifier 53 of Figure 1. The amplifier30| has input terminals 302 and 303, which are connected throughconductors 304 and 305, respectively, to the bridge output terminals II2and H3. The amplifier 30| is supplied with electrical energy through atransformer 308, and includes a pair of relays 306 and 301 which areselectively energized in accordance with the phase of an alternatingsignal potential applied to the input terminals 302 and 303. l

The relay 306 controls the movements of a switch arm 3I0 whichcooperates with a stationary contact 3| I, and the relay 301-controlsthe movement of a switch arm 3I2 which cooperates with a stationarycontact 3I3.

The switch arm 3I0 controls anenergizing circuit for field winding 52and armature 50 of motor 44, which circuit may be traced from the upperterminal of a battery 3 I4,.through a switch blade 3I5 of a manuallyoperable switch 3| 6, a

`contact 3I1, a conductor 3I8, switch arm 3I0,

contact 3II, a conductor 320, field winding 52, armature 50, and groundconnections 32| and 322 to the lower terminal of battery 3I4.

The switch arm 3I2 controls an energizing circuit for field winding 5Iand the armature 50 of motor 44, which may be traced from the upperterminal of battery 3I4 through switch blade 3I5, contact 3I1, conductor3| 8, switch arm 3I2, contact 3I3. a conductor 323, field winding 5I,

19 armature 53, and ground connections 32| and 322 to the lower terminalof battery 3| 4.

The switch blade 3|5 is operable between the stationary contact 3| 1 anda second stationary contact 324. The stationary contact 324 is connectedthrough a conductor 325 to a switch blade 328 oi' a second manuallyoperable switch 321. The switch 321 also includes a pair of stationarycontacts 328 and 329, between which the switch blade 323 is movable.

When the switch 3|8 is operated so that switch blade 3|5 engages contact3||, the motor 44 is under control of the amplifier 30|. When the switchblade 3|5 is moved into engagement with contact 224, the motor 44 isunder control of the manually operable switch 321. If switch blade 3|5is engaging contact 324, and switch blade 326 is moved into engagementwith stationary contact 323, an energizing circuit is completed forileld winding 52 and armature 50 of motor 44 which may be traced fromthe upper terminal of battery 3|4 through switch blade 3|5, contact 324,conductor 325, switch blade 326, contact 328, a conductor 33|, eldwinding 52, amature 50, and ground connections 32| and 322 to the lowerterminal of battery 3|4.

When switch bladeg3|5 engages the contact 324, if switch blade 32B ismoved into engagement with contact 329, an energizing circuit iscompleted for field winding 5| and armature 50 of motor 44 which may betraced from the upper terminal of battery 3|4 through switch blade 3|5,contact 324, conductor 325, switch blade 326, contact 329, a conductor332. fleld winding 5|, armature 50, and ground connections 32| and 322to the lower terminal of battery 3|4.

It should be noted that in the system of Figure 3, the interior ofbellows |53 is connected through a tube 335 to the carburetor at a pointon the upstream side of the throttle 20. In this manner, the controlsystem is not affected by the position of the throttle 20. If thecontroller |52 were made responsive to pressure at a point on thedownstream side of the throttle 20, then the waste gate 3| would try tooperate so as to compensate for all changes in the intake manifoldpressure caused by manual operation of the throttle 20, so that thepilot could not eectively change the intake manifold pressure bymanipulation of the throttle 20.

From the foreging description, it is believed clear that upon anincrease in the pressure in. the carburetor the waste gate motor 44 isenergized in a. direction to open the waste gate and to move the slider41 to the right to rebalance the bridge circuit. Conversely, upon adecrease in pressure in the carburetor I1, the waste Bate motor 44 isenergized for operation in a direction to close the waste gate so as toincrease the speed of the compressor, thereby increasing its compressionratio and hence the pressure in the carburetor In this example, as inthe previous one, the control apparatus recited operates to maintain orchange engine operating variables.

While I have shown and described certain preferred embodiments of myinvention, other modications thereof will readily occur to those skilledin the art, and I therefore wish my invention to be limited only by theappended claims.

I claim:

l. Apparatus for controlling an operating pressure of a combustionengine having at least one combustion chamber with valve meanscontroltake pressure and another of which is adapted'to be positioned bysaid device responsive to outlet pressure, and electrical amplifyingmeans connected to said network and said motor to control the operationof said motor means in accordance with the adjustment of said impedancesin said network.

2. Apparatus for controlling a combustion engine having at least onecombustion chamber and a turbine driven by the products ot combustionflowing from the chamber with valve means controlling the flow of one ofthe components of an ignitable mixture to said chamber, the combinationcomprising, electrical motor means for reversibly positioning the valvemeans, and means for reversibiy energizing said motor in accordance withthe speed of the turbine and magnitude of a further operating variableof said engine, said last named means comprising a balanceableelectrical network of a proportioning type having a plurality ofadjustable impedances, one of which is adapted to be adjusted by adevice responsive to turbine speed and another of which is adapted to bepositioned by a device responsive to said further variable, andelectronic amplifying means connected to said network and said motor toenergize said motor in accordance with the ladjustment of saidimpedances in said networ 3. A system for controlling the pressure ofthe air supplied to the intake of a combustion engine having acompressor for supplying air to said intake, comprising in combination,means for controlling the compression ratio of said compressor,electrically controlled motor means for operating said ratio controllingmeans, a variable impedance device responsive to the pressure in theexhaust oi' said engine, said variable impedance device assuming aconstant value o! impedance over one range of variation of said exhaustpressure and operative over a second predetermined range of variation ofexhaust pressure to vary its impedance, and means including saidvariable impedance device ior controlling said motor means so that oversaid predetermined range of variation said ratio controlling means isoperated proportionately to the value of said pressure.

4. An apparatus for controlling the pressure of the air supplied to theintake of a combustion engine having a compressor for supplying air tosaid intake, comprising in combination, means for controlling thecompression ratio of said compressor, a single electrically controlledmotor means for operating said ratio controlling means, a balanceableelectrical impedance network having a plurality of adjustable impedancestherein, a first device responsive to the pressure oi' the air in theintake connected to and positioning one of said impedances, a deviceresponsive to the speed of said compressor for positioning another ofsaid impedances, amplifying means conadjustable impedances therein,iirst electrically controlled motor means for operating said throttle,second electrically controlled motor means for operating said ratiocontrolling means, both ci said motor means adjusting separateimpedances in said network in accordance with an electrical signal fromsaid network, a control device responsive to the pressure in the intakeo! said engine, said control device adjusting a further impedance insaid network and operating with said network in response to aunidirectional change in said pressure nrst to control one of said motormeans in a mpdulating manner until the device operated thereby hasreached a predetermined position, and thereafter to control the other ofsaid motor means in a modulating manner. l

6. Apparatus i'or controlling the pressure of the air supplied to theintake of a combustion engine having a throttle, a compressor forsupplying air to -said manifold through said throttle,

and means for controlling the compression ratio of said compressor,comprising in combination, iirst motor means for operating saidthrottle, second motor means for operating said ratio controlling means,a balanceable electrical network, variable impedance means connected insaid network, means responsive to the pressure of the air supplied bysaid compressor for,varyin`g said variable impedance means, saidvariable impedance means being capable of producing a relatively largerange of unbalance in said network, rst and second rebalancing meanseach capable of rebalancing said network throughout different portionsof said range of unbalance, a driving connection between said iirstmotor means and said first rebalancing means, means responsive to thepotential diierence between said first rebalancing means and anotherpoint in said network for controlling said ilrst motor means, a drivingconnection between said second motor means and said second rebalancingmeans, and

, means responsive to the potential difference between said point andsaid second rebalancing means for controlling said second motor means.

7. Apparatus for controlling the pressure of the air supplied to theintake of a combustion engine, comprising in combination, a throttle,rst motor means for operating said throttle, a compressor for supplyingair to said intake through said throttle, which compressor incidentallyheats the air passing through it, means for controlling the compressionratio of said compressor, second motor means for operating saidcompression ratio controlling means, a device responsive to the pressureof the air supplied by said compressor, control means for both saidmotor means including said device, said control means normally beingeffective in response to a demand for an increase of pressure in saidintake iirst to operate said throttle to its maximum air ilo`w positionand second to operate said compression ratio controlling means towardits maximum air flow position, and means associated with said controlmeans for causing a movement of said throttle in a iiow decreasingdirection and a substantially simultaneous compensating movement of'saidcompression ratio controlling means in a ilow increasing direction so asto maintain a substantially constant pressure in said intake whileincreasing the temperature therein.

8. Electrical apparatus for controlling the pressure oi' the airsupplied to the intake of a combustion engine, comprising incombination, a throttle, first electrical motor means for operating saidthrottle, a compressor for supplying air tosaid intake through saidthrottle, which compressor incidentally heats the air passing throughit, means for controlling the compression ratio of said compressor,second electrical motor means for operating said compression ratiocontrolling means, an electrical control network including a deviceresponsive to the pressure in said intake, cyclically operating switchmeans for placing said network in control of said first and second motormeans during alternate periods, said network and said two motor meansnormally operating in response to a demand for an increase of pressurein said intake rst to operate said throttle to its maximum air flowposition and second to op-` erate said compression ratio controllingmeans toward its maximum air flow position, and means associated withsaid network and said switch means for introducing an electricalpotential into said network during the periods when said networkcontrols said iirst motor means .to cause movement of said throttle in aflow decreasing direction, said network'consequently operating to causea compensating movement of said compression ratio controlling means in aflow increasing direction to maintain a substantially constant pressurein said intake and to increase the temperature therein due to theincreased heat from said compressor.

9. Electrical apparatus for controlling the pressure of the air suppliedto the intake of a combustion engine, comprising in combination, athrottle, rstv electrical motor means for operating said throttle, acompressor for supplying air to said intake through said throttle, whichcompressor incidentally heats the air passing through it, means forcontrolling the compression ratio of said compressor, second electricalmotor means for operating said compression ratio controlling means, anelectrical 'control network including a device responsive to thepressure in said intake, means responsive to a first potential of saidnetwork for controlling said rst motor means, means responsive to asecond potential of said network for controlling said second motormeans, said network and two motor means normally operating in responseto a demand for an increase of pressure in said intake first to operatesaid throttle to its maximum air iiow position and second to operatesaid compression ratio controlling means toward its maximum air flowposition, and means for supplying an additional potential to said rstmotor controlling means to cause movement of said throttle in a ilowdecreasing direction, said network consequently operating to cause acompensating movement of said compression ratio controlling means in ailow increasing direction to maintain a substantially constant pressurein said intake and to increase the temperature therein due to theincreased heat from said compressor.

10. Apparatus for controllingthe pressure of the air supplied to theintake of a combustion engine, comprising in combination, a throttle,ilrst motor means for operating said throttle, a compressor forsupplying air to said intake through said throttle, which compressorincidentally heats the air passing through it, means for controlling thecompression ratio oi said compressor, second motor means for operatingsaid compression ratio controlling means, a device responsive to thepressure in said intake, control means for both said motor meansincluding said device, said control means normally being effective inresponse to a demand for an increase oi' pressure in said intake firstto operate said throttle to its maximum air ow position and second tooperate said compression ratio controlling means toward its maximum airilow position, and means responsive to the occurrence ot ice-formingconditions to cause a movement of said throttle in a fiow decreasingdirection and a substantially simultaneous compensating movement of saidcompression ratio controlling means in a ilow increasing direction so asto maintain a substantially constant pressure in said intake whileincreasing the temperature therein.

11. Apparatus for controllingl the pressure of the air supplied to theintake of a. combustion engine, comprising in combination, a throttle,rst motor means for operating said throttle, a compressor for supplyingair to said intake through said throttle, which compressor incidentallyheats the air passing through it, means for controlling the compressionratio of said compressor, second motor means for operating saidcompression ratio controlling means, a device responsive to the pressurein said intake, control means for both said motor means including saiddevice, said control means normally being 'etlective in response to ademand for an increase of pressure in saidintake rst tol operate saidthrottle to its maximum air ilow position and second to operate saidcompression ratio controlling means toward its maximum` air flowposition, and means variable in a modulating manner and associated withsaid control means for causing a movement of said throttle in a ilowdecreasing direction and a substantially simultaneous compensatingmovement of said compression ratio controlling means in a ilowincreasing direction so as to maintain a substantially constant pressurein said intake while increasing the temperature therein.

12I Apparatus for controlling the pressure of the air supplied to theintake oi a combustion engine, comprising in combination, a throttle,ilrst motor means for operating said throttle, a compressor forsupplying air to said intake through said throttle, which compressorincidentally heats the air passing through it, means for controlling thecompression ratio of said compressor, second motor means for operatingsaid compression ratio controlling means, a' device responsive to thepressure in said intake, control means for both said motor meansincluding said device, said control means normally being effective inresponse to a demand for an increase of, pressure in saidl intake ilrstto operate said throttle to its maximum air ilow positionlande` pressionratio controlling means in a flow increasing direction so as to maintaina substantially constant pressure in said intake while increasing thetemperature therein, and means responsive to the air temperature at apoint on the discharge side of said compressor for controlling saidvariable means.

13. A system for controlling the pressure in the intake of a combustionengine having a compressor for supplying air to said intake, comprisingin combination, means for controlling the compression ratio of saidcompressor, motor means for operating said ratio controlling means, afirst control device responsive to the pressure of the air supplied bysaid compressor, a second control device which is manually operable, andmeans for selectively placing said motor means under control of one ofsaid control devices sov that when said motor means is under the controlof one of said devices it is completely unaiected by the condition ofsaid other device.

14. Pressure and temperature control means. comprising in combination, achamber in which the pressure and temperature are to be controlled, acompressor for supplying said chamber with a compressible fluid, whichcompressor incidentally heats the fluid passing through it, valve meansfor controlling the now of uid from said compressor to said chamber,means for controlling the compression ratio of said compressor, firstmotor means for operating said valve means, second motor means foroperating said compression ratio controlling means, a device responsiveto the pressure in said chamber, control means for both said motor meansincluding said device, and means associated with said control means forcausing a movement of one of said motor means in a flow increasingdirection and a su.bl stantially simultaneous compensating movement ofthe other of said motor means in a flow decreasing direction, so as tocontrollthe temperature in said chamber without disturbing the pressuretherein.

15. Pressure and temperature control means, comprising in combination, achamber in which the pressure and temperature are to be controlled, acompressor for supplying said chamber with a compressible fluid, whichcompressor incidentally heats the uid passing through it, valve meansfor controlling the ilow of fluid from said compressor to said chamber,means for controlling the compression ratio of said compressor, firstmotor means for operating said valve means, second motor means foroperating said compression ratio controlling means, a device responsiveto the pressure in said chamber, control means for both said motor meansincluding said device, a device responsive to the temperature of thefluid at a point on the discharge side of said compressor, and y[meansincluding said device associated with said control means and operativelto cause a movement of one of said motor means in a flow increasingdirection and a substantially simultaneous compensating movement oi' theother of said motor means in a flow decreasing direction, so as tocontrol the temperature in said chamber without disturbing the pressuretherein.

16. In a proportioning system, in combination, a followup systemincluding a controller for operating the system in a manner to require apredetermined amount of followup action, a first device to beproportionally positioned, followup means operated thereby operative toprovide only a portion of the followup action required by the systemunder the control of said controller, a second device to beproportionally positioned, a second followup means operated therebyoperative to provide a different portion of the followup action requiredby said system under the control of said controller, and a selectivelyoperable controller connected to modify the effect of said first namedcontroller upon one of said devices so that said one device will providea followup action over the same portion as that provided by said otherdevice.

17. Electrical control apparatus, comprising in combination, acontroller, a first and second control devices to be positioned inaccordance with the operation of said controller, a first variableimpedance means operated by said controller, a separate followupvariable impedance means associated with each control device andadjusted thereby, an electrical network including said variableimpedance means with said followup impedance means connected in seriestherein, means responsive to a first potential of said networkcontrolled by said first variable impedance means and a followupimpedance means adjusted by said first device for controlling said firstdevice, and means simultaneously responsive to a second potential ofsaid network controlled by said first variable means and followup meansadjusted by said second device for Acontrolling said second device, bothof said responsive means having continuous electrical connectionsto'said network.

18. Apparatus for controlling the pressure of the air supplied to theintake of a 4combustion engine, comprising in combination, a throttle,first motor means for operating said throttle, a compressor forsupplying air toI said -intake through said throttle, which compressorincidentally heats the air passing through it, a turbine powered by theexhaust gases from said engine for driving said compressor, means forcontrolling the flow of exhaust gases from said engine through saidturbine by controlling the pressure of said gases, second motor meansfor operating said flow controlling means, a first control deviceresponsive to the pressure of the air supplied by said compressor,control means for both said motor means including said first controldevice, means associated with said control means for causing a movementof one of said motor means in a flow increasing direction and asubstantially simultaneous compensating movement of the other of saidmotor means in a flow decreasing direction, and a second control deviceresponsive to the pressure of said exhaust gases, said second controldevice being associated with said control means and effective when saidexhaust gas pressure exceeds a predetermined value to cause said secondmotor means to run in a direction to decrease said exhaust gas pressure.

19. In a balanced bridge circuit, in combination, a controller forunbalancing said bridge circuit throughout a predetermined range, meansresponsive to unbalance of the bridge circuit, means for rebalancingsaid bridge circuit, a first power means controlled by said unbalanceresponsive means for operating said rebalancing means in a manner torebalance said bridge only for a portion of the range of unbalanceproduced by said controller, a second power means controlled by saidunbalance responsive means for operating said rebalancingv means in amanner to rebalance said bridge for a different portion of the range ofunbalance produced by said concontroller upon one of said power means sothat said one power means will rebalance said bridge circuit over arange which includes a part of the range where the other of said powermeans is effective to rebalance said circuit.

20. In combination, a turbosupercharger actuated by exhaust gases, valvemeans for regulating the flow of exhaust gases to the turbine, a motorfor controlling said valve means. and means responsive to apredetermined pressure appurtenant to an operating condition of saidsupercharger for positioning said valve means to maintain saidpredetermined pressure at a substantially constant value over apredetermined range of operation comprising a plurality of unitsinterconnected solely by electrical leads including a manual pressuresetting means, a pressure unit mounted adjacent said pressure to beregulated, and an amplifier responsive to changes in the pressure to beregulated for amplifying said pressure changes arranged to control saidmotor.

2l. In combination, a turbosupercharger actuated byr exhaust gases, awaste gate for regulating the flow of exhaust gases to the turbine, anelectric motor for positioning said waste gate, means for controllingthe energization of said motor to position said waste gate and maintainconstant a predetermined pressure appurtenant to an operating conditionof said supercharger including an electronic amplifier responsive tochanges in said predetermined pressure for amplifying said changes insaid predetermined pressure for controlling said motor, and meansresponsive to speeds above a predetermined maximum speed ofsaid'supercharger for taking over control of said amplifier andpreventing said maximum speed from being exceeded.

22. In a balanced bridge circuit, in combination, a controller capableof producing a relatively large range of unbalance in said bridgecircuit, a pair of rebalancing devices each capable of rebalancing saidbridge circuit throughout different portions of said range of unbalancebut individually incapable of rebalancing said bridge circuit throughoutthe complete range of unbalance which said controller is capable ofproducing, means responsive to unbalance in said bridge circuit foroperating said devices, and a selectively variable signal sourceconnected in said circuit to modify the action of said controller uponone of said rebalancing devices to effect simultaneous movement of saidone device and the other of said devices over a common range ofunbalance.

23. In combination, an engine, a plurality of regulating means for theengine, an electric motor for each regulating means for positioning it,an automatic control device responsive to a force which is a measure ofengine power output, and means for causing said control device tocontrol said motors in sequence to effect sequential operation of saidregulating'means as the value of said force changes, said last namedmeans including continuously maintained electrical connections betweensaid device and said motors so that said motors can move simultaneouslyif the value of said force changes in a predetermined manner such as torequire movement of both motors.

24. Control apparatus for a combustion enginel having a compressor andthrottling means, comprising in combination, compression ratiocontrolling means, first motor means adjusting said 27 ratio controllingmeans, second motor means adjusting the throttling means, currentcontrolling means actuated by means responsive to an operating pressureof said engine, means including said current controlling means forcausing reverse energization of only said ilrst motor means when theoperating pressure is in a ilrst range of values, means including saidcurrent controlling means for causing reverse energization of only saidsecond motor means when the operating pressure is in a second range ofvalues. and means connecting said current controlling means to saidfirst and second motor means to effect simultaneous energization of bothof said motor means when the operating pressure changes in apredetermined manner such. as to require movement of both o1 said motormeans.

25. In a control for a combustion engine having a compressor, thecombination comprising, means for regulating the compressing effect ofthe compressor, an electric motor for positioning said regulating means,means controlling the energization of said motor to position saidregulating means to maintain constant a predetermined operating variableof said engine includlng an electronic amplier responsive to changes insaid predetermined variable for amplifying said changes for controllingsaid motor, and means responsive to the speed of said compressor fortaking over control oi said amplitler to maintain the speed of saidcompressor within predetermined limits.

26. In a control for a combustion engine having a compressor therefor,the combination comprising. means for regulating the compressing eil'ectof said compressor, a motor for controlling said regulating means, andmeans responsive to a predetermined variable operating pressure of saidengine for positioning said regulating means to maintain saidpredetermined pressure at a desired value comprising a plurality ofunits interconnected solely by electrical leads includlng a manualpressure `setting means, a pressure responsive unit, and an amplifierresponsive to changes in the pressure to be regulated for amplifyingsaid pressure changes arranged to control said motor.

27. In a control apparatus, electric motor means, a proportioningcontrol for energizing said motor in a predetermined manner and havingrebalancing means positioned by said motor. rst manual means l'oradjusting the eil'ect of said control upon said motor, a source ofpower,

ailoating control for energizing said motor com prising a manuallypositioned double throw 28 switch means, said manually positioned switchmeans arranged to connect said source to drive said motor in onedirection or the other. and selectively operable switch means forconnecting one or the other of said controls to said motor so that whenunder the control of one of said controls the motor is completelyunaffected by the condition of said other control.

28. Apparatus for controlling the pressure of the air supplied to theintake of a combustion engine having a compressor for supplying air tosaid intake. means for controlling the compressing eilect of saidcompressor, a single electrically controlled motor means for positioningsaid means for controlling the compressing eflect, current controllingmeans for controlling the operation of said single motor means, a irstdevice responsive to the pressure of the air supplied by saidcompressor, a second device responsive to the speed of said compressor,and means including both said devices for controlling the operation ofsaid current controlling means.

HUBERT T. SPARROW.

f REFERENCES CITED The following references are of record in the ille ofthis patent:

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